Thanks for replies!
Yes, this could very well be a problem of pin multiplexing. From looking at
the Kilauea GPIO/Pin mux configuration in U-Boot, GPIO30 is configured as GPIO
input and not as IRQ1. So this can't work. The easiest way to change this is
in U-Boot (include/configs/kilauea.h).
BTW: Are you using Kilauea or a custom 405EX board?
Best regards,
Stefan